Along with his older brother John, he developed his game under the tutelage of noted black golf instructor Lucius Bateman whose other students included PGA Tour winners Don Whitt, John McMullin, and Tony Lema.

He shot a record-breaking 59 in the final round of the 1963 Santa Clara County Golf Championship, which still stands.

As an amateur, Lotz captured the 1960 and 1963 Alameda Commuters golf tournament, 1961 and 1962 California State Fair events, the 1962 and 1963 Stanford Invitationals, 1963 Oakland City, 1963 Santa Clara County championship, 1963 Far Western Junior Intercollegiate championship, and most notably, the 1962 California State Amateur.

Before declaring their intention to turn professional, both Lotz brothers were ranked among the nation's Top Ten Amateurs in 1963 by Golf Digest magazine.

That performance earned Lotz Golf Digest's Most Improved Golfer award, along with selection by its editorial panel of experts of those most likely to capture a major in 1971.